I’ve got several rubber rock molds I used on my previous HO layout back in the early '90s. I have not “made a rock” since then, and forgot what release agent I used. Soooo, as the title says, “What release agent do you use?”
As I did on the previous layout, I will both apply the mold directly to the plaster surface and release it “when it got hot”, and I’ll pour some (smaller ones) and let them harden in the mold and attach them to the plaster surface with a brushing of plaster - or caulk.
Any other pointers you might have would be appreciated. What I did way back when actually turned out pretty nice, but it was a long time ago.
I give them a spritz of wet water before poring the hydrocal.
The only tip I can offer is a good cleaning after and store them in a plastic bag with a little baby powder in them to make them last for the next time
Wet water for me, too. I “liberated” a spray bottle from my wife. 2 drops of dishwashing liquid in the bottle does the trick. I’m using Hydrocal for my castings.
I’ll add my vote for “wet water” also. I tried other agents but the water seems to work the best. It is critical that you thoroughly clean the molds between uses since small bits of plaster may stick in the mold and interfere with your later castings.
Some of my rocks are made with hydrocal. For those I use wet water in the mold.
Some of my rocks are made with dental stone. For those I use Pam cooking spray in the mold.
The dental stone is much stronger, but must be painted. The hydrocal is lighter and more brittle but stains very realistically with VERY diluted water based paint.
I’ll definitely cast my vote for ‘wet’ water (2 or 3 drops of liquid detergent added to water in a spray bottle). I generally use a thinned ‘wetter’ Sculptamold for my rock castings–hydrocal sets up too fast in my dry garage climate out here. It’s a slower process, but it works for me, and the resulting rock surfaces have the ‘grit’ of Sierra granite. But whatever you use–plaster, hydrocal, etc., make sure that you scrub the mold out after. I use liquid detergent and an old toothbrush, then store them in plastic bags. I’ve got rock molds over 20 years old that I can still use.
I realize that I will be refering to the “Second Ice Age” here, but when I was in art school (in the late sixties) we all took a class Freshman year called “Plaster Workshop,” in which we learned the “do’s and don’t” of mold making, and started out casting plaster parts in plaster molds (either it is gonna release or it isn’t.) For a mold release we used a liquid acquired at the drug store called “Tincture of Green Soap.” We painted it on the inside of the mold, let it dry, and then poured the plaster in. Sometimes the mold got broken during the “de-molding” procedure. [banghead] Lesson? Make a mold from which you can cast new molds so you can replace them if you break one … and use hydrastone for that mold!
All of my rock molds are Latex molds (four or five layers of Latex, reinforcing gauze strips, and another five or six layers of Latex) which I pulled from rocks indigenous to northeastern Pennsylvania that have the miniaturized look of 1:1 scale strata . I used the Tincture of Green Soap generously in the making of the molds! I generally do not need much of a mold release on the Latex molds as I was careful when making them not to permit any undercuts (simply … places where the part will not easily just slip straight out of the mold.) I have had no problems casting exposed rock faces for cuts through hills or on mountainsides.
Gee I only used water to wet and wash the molds before use and poured in the WS plaster and let it harden before I peeled off the mold. I made several castings from the same molds. MAybe I was lucky they didn’t stick? And I never tried to peel it off before it fully hardened?
ALSO NEVER wash your plaster stuff down the sink drain!! SOme one I know {not me, but I would call him “idiot” for short} decided to clean up wet plaster stuff in the sink and it clogged and hardened in his drain. [banghead]